Mobile communication systems use cellular networking cell system. Frequency reuse-based cellular networking cell system improves system capacity and implements broad network coverage in a real sense. A terminal establishes a connection with a network cell through an access procedure and obtains communication services. When the terminal moves and spans the cell, a handover procedure is required to switch communication services between the terminal and the original cell to a new cell, ensuring uninterrupted communication. As shown in FIGS. 1 and 2, schematic diagrams of the traditional wireless air interface access procedure and wireless air interface handover procedure used still in the third generation mobile communication system (3G) and the fourth generation mobile communication system (4G) presently are provided. Step 1 to step 3 in FIG. 1 and step 3 to step 5 are a type of random access. In 4G, there are 5 scenes (A, B, C, D and E) for the random access, which represent reasons for 5 accesses:
A. Initial access initiated from RRC_IDLE (Radio Resource Control_IDLE)
B. Initial access initiated after failure of wireless links
C. Random access during handover
D. Downlink data arrival under RRC_CONNECTED (Radio Resource Control_CONNECTED)
E. Uplink data arrival under RRC_CONNECTED
The 5 scenes described above can be distinguished by signaling contents of step 3 in FIG. 1 or step 5 in FIG. 2.
In order to further improve spectrum utilization, starting from 3G, mobile communication systems tend to use the whole network cellular cell co-channel networking, in which all cells use same frequency resources. However, even so, co-channel interference occurs between adjacent cells, and the co-channel interference is the most serious in edge areas at the boundary of the adjacent cells, i.e., handover areas. The cell edge, which is supposed to be a weak signal field where path loss may be large, coupled with the co-channel interference between the adjacent cells, makes wireless channel condition worse and signal interference noise ratio (SINR) lower. According to the basic principle and procedure of handover, a terminal usually sends measurement reports to the original cell only when the terminal has already arrived at the coverage area of the new cell and signals in the new cell have already been stronger than those in the original cell. Then the terminal waits for a handover command from the original cell and hands over to the new cell after receiving the handover command, see FIG. 2. In this handover process, step 1 and step 2 are actually the stages when the co-channel interference is most serious and communication channel quality is worst.
Because, in principle, all channel resources are based on shared scheduling, service type of 4G is more simplified than 3G. There is only one service, packet service (PS), in 4G, therefore, wireless air interface signaling of 4G is much more simplified than that of 3G. Whether the procedure is an access procedure or a handover procedure, it can be classified as configuration of RRC connection, including establishment, reestablishment and reconfiguration of RRC connection. For the five random accesses described above, the random accesses in the three scenes A, D and E correspond to “RRC connection establishment request”, the random access in the scene B corresponds to “RRC connection reestablishment request”, and the random access in the scene C corresponds to “RRC connection reconfiguration completion”. In addition, since a 4G terminal can detect adjacent cells itself, unlike 3G, a 4G cell does not need to send information of the adjacent cells to the terminals.
Although 4G signaling is much simpler than 3G signaling, for cellular cell networks in dense urban, mixed signals result in frequent signaling interaction between terminals and cells, which brings a lot of signaling overheads and co-channel interferences to 4G networks. Moreover, characteristics such as online forever and burstness of 4G data services also increase signaling interaction between terminals and cells easily, resulting in what is commonly known as “signal storm” in the industry.
At present, co-channel interference, signaling overhead, resource energy loss and service performance (e.g., uplink throughput and downlink throughput) in handover areas at the cellular cell edge under co-channel networking, which have become acknowledged shortcomings in 3G and 4G co-channel networking, are the focus of common concern of technical research, standard evolution and industry development.